The present invention relates to a liquid flow control system for use with infusion sets of the type comprising a liquid supply, a drip chamber downstream of the liquid supply for forming liquid drops and a flexible tube connecting the drip chamber with an injection needle, the system comprising a drop sensor adapted for being arranged adjacent the drip chamber for sensing the passage of drops through the drip chamber, a valve adapted for controlling the flow of the liquid through the tube valve activating means for activating the valve, electrical circuits for registering the rate of drop formation and controlling the valve activating means, and a battery for powering the drop sensor, the electrical circuits and the valve activating means.
In connection with infusion sets it is known to monitor the rate of formation of drops in a drip chamber by means of drop sensors connected to programmable controllers that can calculate the rate of drop formation and compare it with a set value. Such systems are disclosed in U.S. Pat. No. 5,938,543, U.S. Pat. No. 5,045,069, U.S. Pat. No. 4,346,606 and U.S. Pat. No. 4,583,975, the disclosures of which are hereby incorporated herein by reference.
U.S. Pat. No. 4,634,426, U.S. Pat. No. 4,775,368 and U.S. Pat. No. 4,038,982, the disclosures of which are hereby incorporated herein by reference, disclose drop monitor means connected to a controller that again is electrically connected to a separate valve means or occlusion means attached to the flexible tube leading from the drip chamber to the infusion needle of the infusion set. The valve means or occlusion means vary the flow of liquid through the flexible tube so that the set rate of drop formation can be complied with.
As the liquid flow control systems known in the art thus comprise 2-3 separate individual units interconnected by electrical wires and needing to be mounted separately, the known systems are difficult to apply to the infusion sets, the connecting wires may become entangled with other objects or disconnected entailing failure of the system, and the mounting procedure is prone to errors leading to malfunction of the system.